Improved low-voltage reactive power compensation device

Abstract

The utility model discloses an improved low-voltage reactive power compensation device, which belongs to the technical field of power, and comprises a magnetic balance coil, a compensation capacitor, an inductor and a transformer, according to the technical scheme, the compensation efficiency of a capacitor is improved: when a fundamental current flows through a traditional capacitor and a series reactor, the reactor can offset the capacity of the capacitor, so that the actual output capacity of compensation equipment is far lower than the rated capacity, and the use efficiency of the capacitor is reduced. The asymmetric magnetic ring coil is adopted, power frequency current impedance is close to zero due to the offset effect of a magnetic circuit, the compensation efficiency of the capacitor is greatly improved, and the size, loss and cost of a series reactor are reduced; and the volume, the loss and the cost of the series reactor can be greatly reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power, and more specifically, to an improved low-voltage reactive power compensation device. Background Art

[0002] In a power system, due to the existence of a large number of inductive loads, the power factor of the system will be reduced, bringing a series of adverse effects, such as a decrease in the energy conversion efficiency of the system, an increase in the power transmission line loss of the power grid, an increase in the internal loss of power equipment, a force adjustment fine imposed on relevant enterprises, and a waste of power resources. Using power capacitors for reactive power compensation is one of the common measures to improve the power factor.

[0003] However, capacitive compensation is easily affected by harmonics in the power system. To suppress harmonic current from flowing into the capacitor, a series reactor is usually used in combination. However, the use of a series reactor has some problems. For example, it will offset the actual compensation of the capacitor, resulting in a significant reduction in the effective output capacity of the compensation device; when using an iron-core reactor, due to the low magnetic permeability of the iron core, the number of turns required for the reactor coil is large, resulting in a large volume of the reactor; the iron-core reactor has high losses, and special temperature control and heat dissipation are required for heat generation, resulting in an increase in power consumption; the cost is high, the consumption of iron core and copper wire is large, and the cost is much higher than that of the capacitor itself.

[0004] Therefore, an improved low-voltage reactive power compensation device is proposed for the above problems. Content of the Utility Model

[0005] In order to overcome the deficiencies of the prior art, the purpose of the utility model is to provide an improved low-voltage reactive power compensation device, by improving the compensation efficiency of the capacitor: in the traditional method of adding a series reactor to a capacitor, when the fundamental wave current flows through, the reactor will offset the capacity of the capacitor, resulting in the actual output capacity of the compensation device being much lower than the rated capacity, reducing the use efficiency of the capacitor. The present invention uses an asymmetric magnetic ring coil, and the impedance to the power frequency current is close to zero due to the cancellation effect of the magnetic circuit, greatly improving the compensation efficiency of the capacitor.

[0006] The above technical purpose of the utility model is achieved through the following technical solutions:

[0007] An improved low-voltage reactive power compensation device includes a magnetic balance coil, a compensation capacitor, an inductor, and a transformer;

[0008] The capacitive branch generates capacitive current, and the inductive branch outputs voltage inductive current through the transformer. The phases of the currents are 90° ahead of and lagging behind the phase of the system voltage respectively.

[0009] Refer to Figure 1 - Figure 2As shown, the magnetic balance coil is a magnetic ring coil with high magnetic permeability. The primary winding is connected to a current, and the secondary winding is connected to a current. The turn ratio of the primary and secondary windings is 1:n;

[0010] In this solution, when applying the system voltage alternating voltage Un, a capacitive current I1 is generated in the capacitive branch, and an inductive current I2 is output through the transformer in the inductive branch. The phases of I1 and I2 lead and lag the phase of the system voltage Un by 90° respectively, that is, their phases are exactly opposite.

[0011] Refer to Figure 1 - Figure 2 As shown, f = 50Hz, and the value of the selected inductor is matched with the capacitance value of the compensating capacitor. The fundamental wave current := n:1.

[0012] Refer to Figure 1 - Figure 2 As shown, the magnetic fluxes generated by the current in the magnetic ring and the current in the magnetic ring are equal in magnitude and opposite in direction. The magnetic fluxes cancel each other out, reaching a state of magnetic circuit balance. The impedance of the magnetic balance coil in the capacitive and inductive branches is zero.

[0013] Refer to Figure 1 - Figure 2 As shown, in the harmonic state, the capacitive reactance value of the capacitor = 1 / , and the inductive reactance value of the inductor is = kXL. Under the same voltage condition, the harmonic current := k2:1. The magnetic fluxes generated by and in the magnetic ring no longer cancel each other out;

[0014] In this solution, in the case of power frequency fundamental wave current, when I1:I2 = n:1 is satisfied, the magnetic fluxes generated by the current I1 in the magnetic ring and the current I2 in the magnetic ring are equal in magnitude and opposite in direction. The magnetic fluxes cancel each other out, reaching a state of magnetic circuit balance. At this time, the impedance of the magnetic balance coil in the capacitive and inductive branches is zero, which is equivalent to presenting zero impedance to the fundamental wave current.

[0015] Refer to Figure 1 - Figure 2 As shown, the harmonic current of the primary side winding in the magnetic core is relatively large, and the magnetic balance coil presents a large series inductance to the capacitive compensation branch.

[0016] In summary, the present utility model has the following beneficial effects:

[0017] (1) By improving the compensation efficiency of the capacitor in this solution: In the traditional method of adding a series reactor to the capacitor, when the fundamental wave current flows through, the reactor will cancel the capacitance of the capacitor, resulting in the actual output capacity of the compensation device being much lower than the rated capacity, reducing the utilization efficiency of the capacitor. The present invention adopts an asymmetric magnetic ring coil, and the impedance to the power frequency current is close to zero due to the cancellation effect of the magnetic circuit, greatly improving the compensation efficiency of the capacitor.

[0018] (2) This solution reduces the volume, loss, and cost of the series reactor: By using a magnetic ring inductor with high magnetic permeability to replace the traditional iron-core reactor, the volume, loss, and cost of the series reactor can be significantly reduced. It can greatly improve the integration of the capacitor module, with a smaller module having a larger capacity and lower system loss.

[0019] (3) This solution enhances the harmonic suppression effect: The novel reactive power compensation circuit of the present invention has more excellent "harmonic blocking and fundamental wave passing" performance, with extremely low impedance for power frequency fundamental wave current, high system efficiency, and high impedance for high-order harmonic current, resulting in better harmonic suppression effect. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of the principle of the unidirectional capacitor compensation branch in this embodiment;

[0021] Figure 2 It is a schematic diagram of the overall circuit structure in this embodiment.

[0022] Reference numerals in the figure: H, magnetic balance coil; C, compensation capacitor; L, inductor; T, transformer. Detailed Embodiment

[0023] The following further describes the present utility model in detail with reference to the accompanying drawings.

[0024] Among them, the same components are denoted by the same reference numerals. It should be noted that the terms "front", "rear", "left", "right", "upper", and "lower" used in the following description refer to the directions in the drawings, and the terms "bottom surface" and "top surface", "inner" and "outer" respectively refer to the directions towards or away from the geometric center of a specific component.

[0025] Refer to Figure 1 - Figure 2 As shown, a modified low-voltage reactive power compensation device in a preferred embodiment of the present utility model includes a magnetic balance coil H, a compensation capacitor C, an inductor L, and a transformer T;

[0026] The capacitor branch generates capacitive current I1, and the inductor branch outputs inductive current I2 through the transformer. The phases of current I1 and current I2 lead and lag the phase of the system voltage Un by 90° respectively.

[0027] Refer to Figure 1 - Figure 2 As shown, the magnetic balance coil H is a magnetic ring coil with high magnetic permeability, and the primary winding is connected to current I1, and the secondary winding is connected to current I2. The turn ratio of the primary and secondary windings is 1:n;

[0028] Under the condition of applying the system AC voltage Un, a capacitive current I1 is generated in the capacitive branch, and an inductive current I2 is output through the transformer in the inductive branch. The phases of I1 and I2 lead and lag behind the phase of the system voltage Un by 90°, respectively, that is, the phases of the two are exactly opposite.

[0029] Refer to Figure 1 - Figure 2 As shown, f = 50Hz, and the value of the inductor L is selected to match the capacitance value of the compensation capacitor C. The fundamental current I1: I2 = n: 1.

[0030] Refer to Figure 1 - Figure 2 As shown, the magnetic fluxes generated by the current I1 in the magnetic core and the current I2 in the magnetic core are equal in magnitude and opposite in direction, and the magnetic fluxes cancel each other out, reaching a state of magnetic circuit balance. The impedance of the magnetic balance coil in the capacitive and inductive branches is zero.

[0031] Refer to Figure 1 - Figure 2 As shown, in the harmonic state, the capacitive reactance value of the capacitor Xc' = 1 / kXc, and the inductive reactance value of the inductor is XL' = kXL (k is the harmonic order). Under the same voltage condition, the harmonic current I1': I2' = k2: 1, and the magnetic fluxes generated by I1' and I2' in the magnetic core no longer cancel each other out;

[0032] In the case of the power frequency fundamental current of this solution, when I1: I2 = n: 1 is satisfied, the magnetic fluxes generated by the current I1 in the magnetic core and I2 in the magnetic core are equal in magnitude and opposite in direction, and the magnetic fluxes cancel each other out, reaching a state of magnetic circuit balance. At this time, the impedance of the magnetic balance coil in the capacitive and inductive branches is zero, which is equivalent to presenting zero impedance to the fundamental current.

[0033] Refer to Figure 1 - Figure 2 As shown, the harmonic current I1' of the primary winding in the magnetic core is relatively large, and the magnetic balance coil presents a large series inductance to the capacitive compensation branch I1'.

[0034] Specific implementation process: First, when applying the system voltage alternating voltage Un: A capacitive current I1 is generated in the capacitive branch, and an inductive current I2 is output through the transformer in the inductive branch. The phases of I1 and I2 lead and lag behind the phase of the system voltage Un by 90° respectively, that is, the phases of the two are exactly opposite. The magnetic balance coil is a magnetic ring coil with high magnetic permeability. The primary winding is connected to the current I1I1 = Un / Xc, where Xc = 1 / (2πfC), and the secondary winding is connected to the current I2I2 = U2 / XL, where XL = 2πfL. The turn ratio of the primary and secondary windings is 1:n. Under the condition of the power frequency fundamental wave f = 50Hz, the value of L is selected to match the capacitance value of the capacitor, so that the fundamental wave currents I1:I2 = n:1. When I1:I2 = n:1 is satisfied, in the case of the power frequency fundamental wave current, the magnetic fluxes generated by the current I1 in the magnetic ring and the magnetic flux generated by I2 in the magnetic ring are exactly equal in magnitude and opposite in direction, and the magnetic fluxes cancel each other out, reaching the state of magnetic circuit balance. At this time, the impedance of the magnetic balance coil in the capacitive and inductive branches is zero, which is equivalent to zero impedance to the fundamental wave current. In the harmonic state, the capacitive reactance value of the capacitor is Xc' = 1 / (kXc), and the inductive reactance value of the inductor is XL' = kXL, where k is the harmonic order. Under the same voltage conditions, the harmonic currents I1':I2' = k2:1, and the magnetic fluxes generated by I1' and I2' in the magnetic ring no longer cancel each other out, and the harmonic current I1' in the primary winding of the magnetic core is larger. At this time, the magnetic balance coil presents the characteristic of a large series inductor to the capacitive compensation branch I1', thereby suppressing the harmonic current in the capacitive branch.

[0035] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. An improved low-voltage reactive power compensation device, characterized in that: It includes a magnetic balance coil (H), a compensation capacitor (C), an inductor (L) and a transformer (T); The capacitor branch generates a capacitive current (I1), and the inductor branch outputs a voltage-inductive current (I2) through a transformer, wherein the phases of the current (I1) and the current (I2) are respectively 90° ahead and 90° behind the phase of the system voltage (Un).

2. The improved low-voltage reactive power compensation device according to claim 1 is characterized in that: The magnetic balance coil (H) is a magnetic ring coil with high magnetic permeability, and the primary winding is connected to the current (I1), and the secondary winding is connected to the current (I2), and the turn ratio of the primary winding and the secondary winding is 1:n.

3. The improved low-voltage reactive power compensation device according to claim 1 is characterized in that: The f=50 Hz, and the value of the inductor (L) is selected to match the capacitance of the compensation capacitor (C), and the fundamental current (I1):(I2)=n:

1.

4. The improved low-voltage reactive power compensation device according to claim 1 is characterized in that: The magnetic flux generated by the current (I1) in the magnetic ring and the magnetic flux generated by the current (I2) in the magnetic ring are equal in magnitude and opposite in direction, the magnetic fluxes cancel each other out, a state of magnetic circuit balance is achieved, and the impedance of the magnetic balance coil in the capacitance and inductance branches is zero.

5. The improved low-voltage reactive power compensation device according to claim 1 is characterized in that: In the harmonic state, the capacitive reactance value of the capacitor (Xc') = 1 / (kXc), and the inductive reactance value of the inductor is (XL') = kXL (k is the harmonic order), and under the same voltage conditions, the harmonic current (I1'): (I2') = k2: 1, and the magnetic fluxes generated by (I1') and (I2') in the magnetic ring no longer cancel each other out.

6. The improved low-voltage reactive power compensation device according to claim 1 is characterized in that: The harmonic current (I1') of the primary winding in the magnetic core is relatively large, and the magnetic balance coil presents a relatively large series inductance to the capacitance compensation branch (I1').

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